1. Field of Invention
The invention concerns an anchor device to which a downhole tool such as a whipstock and casing bit assembly may be preattached, supported and lowered, together as unit by connection to a drill string, in a single trip for attachment to a well bore casing and various purposes such as side tracking or deviating the bore.
In particular the anchor device is of the type in which a mechanical firing means ignites a self contained cartridge of fluid pressure generating material. The fluid pressure acts against a piston, fluid and piston to shear a pin, displace a tapered mandrel and radially displace slips into gripping engagement with the side wall of the well bore casing or well bore.
2. Description of the Prior Art
Heretofore, downhole tools of various types have been anchored to a well casing after a number of trips into the bore by radially expandable slips actuated by various self contained fluid pressure generating devices. The fluid pressure is usually generated by igniting combustible material of various types including explosives, and chemically reactive ingredients adapted to produce fluid pressure of sufficient magnitude to actuate the device. Various means for igniting and mixing the materials are known including electrically and mechanically fired explosive charges, bullets, and other projectiles.
The Applicant's anchor differs from the prior art in that it allows for preattachment of the downhole tool thereto for a single trip by drill string into the bore for attaching the entire assembly to the casing. Also, a preloaded mechanical firing mechanism includes a trigger foot that forcefully engages the bottom or plug in the well bore and which under the weight of the assembly applied thereto, shears pins and releases a preloaded hammer. The hammer strikes and propels a firing pin into the igniter of a cartridge of combustible material which forms to generate the fluid pressure and radially expand the anchoring slips into gripping contact with the casing.